At present, the heat storage and transfer mediums used in the technology of industrial energy storage and high temperature solar heat storage mainly includes air, water, conduction oil, molten salt, sodium, aluminum etc metals. Due to the wide operating temperature range, low vapor pressure, low viscosity, good stability, low cost and other features, molten salt has become a potential heat storage and transfer medium in solar-thermal power generation technology, and it is currently applied more and more mature. The high-temperature molten salt mainly includes nitrate, carbonate, sulphate, fluoride, chloride, oxide, etc.
The prominent advantages of nitrate molten salt are as follows: the source of raw material is wide, the cost is low, and the corrosiveness is low. Compared with other molten salts, nitrate molten salt has great advantages. However, the heat of dissolution and thermal conductivity of molten nitrate are low; namely, the molten nitrate is easy to be decomposed at high temperature. In the existing technology, the researchers tried to add other components to the molten nitrate system to solve the problem mentioned above, but the lower limit working temperature of the molten nitrate system improved is improved while improving the upper limit working temperature, and therefore the maintenance cost of obnubilation is increased. Alkali carbonate, featured with high melting point, good thermal stability and high upper application temperature limit, is the first selection of molten salt in the range of solar heat utilization. However, the lower application temperature limit is improved correspondingly, and the maintenance cost is high due to the energy consumption. For the molten villiaumite, the latent heat of phase change is high, and the heat storage medium with different temperature of phase change can be obtained by mixing the villiaumite with different melting point, and therefore the requirements of space solar thermal dynamic power generation cycle can be met in a wide temperature range. Villiaumite can meet the requirements on thermal performance and compatibility, but there is an obvious disadvantage that the thermal conductivity is low and the volume is shrunk largely while solidifying.
In the prior art, there is no the molten salt system which can meet relatively high upper limit working temperature and low limit lower working temperature while keeping the relatively high thermal conductivity.